1. Field of the Invention
The present invention generally relates to image sensors, and particularly to a color filter of an image sensor, capable of improving shapes of respective unit color cells to closely form various color patterns (such as, a red color pattern, a green color pattern and a blue color pattern) within each unit color cell in a stripe type, thereby normally realizing various colors (such as, red, green and blue) required for image generation by itself without interdependence of the respective unit color cells, so that it is possible to induce a finally finished color filter array to smoothly express more colors within a given condition. Further, the present invention relates to an image sensor using such a color filter and a method for manufacturing an image sensor.
2. Description of the Related Art
Recently, with a rapid development of the electric/electronic technologies, various electronics, such as video cameras, digital still cameras, minicams adapted to personal computers (PC), minicams adapted to mobile phones and so forth, employing image sensor technologies have been widely developed and used.
Traditionally, charge coupled devices (CCDs) have been used in conventional image sensors. However, CCDs can involve drawbacks which may include high driving voltages, separate additional support circuits, and high per-unit prices. As a result, their usage in imaging sensors recently has been declining.
Recently, attention has turned to Complementary Metal Oxide Semiconductor (CMOS) image sensors for overcoming the disadvantages of the CCD. Since CMOS image sensors are manufactured based on CMOS circuit technologies, contrary to existing CCDs, they may have advantages including low driving voltage, lack of additional support circuits, low per-unit price, etc.
As shown in FIG. 1, a CMOS image sensor 10 according to the conventional art for realizing a color image may be constructed in the following manner. Photosensitive pixel units 30 may be combined with a color filter array CA, wherein the photosensitive pixel units 30 may be disposed on a semiconductor substrate 40 and receive light L to generate and accumulate photocharges, and the color filter array CA may force the received light L to be colorized and transmitted to the photosensitive pixel units 30. In this case, in order to transmit light L to the photosensitive pixel units 30 through the color filter array CA, an intermediate layer 20 is interposed between the photosensitive pixel units 30 and the color filter array CA.
Here, as shown in the FIG. 1, the color filter array CA may be combined by a plurality of unit color cells C1, C2, and C3, which may be associated with various colors, such as red, green and blue (in FIG. 1, for the sake of convenience, only four unit color cells are shown). Each of the unit color cells C1, C2 and C3 may be arranged on the top of the intermediate layer 20 in a mosaic type.
Various processes may be performed in conjunction with the use of CMOS image sensor 10. For example, first, the green unit color cell C3, the red unit color cell C1 and the blue unit color cell C2 may colorize light incident L into green, red and blue light, respectively, and then may pass the colorized light to the photosensitive pixel units 30. Subsequently, the respective photosensitive pixel units 30, which may correspond to the green unit color cell C3, the red unit color cell C1 and the blue unit color cell C2, generate photocharges corresponding to the colorized light and then transmit the generated photocharges to signal processing circuits (e.g., interpolation circuits which are not shown). The interpolation circuits then may interpolate the colors of green, red and blue in a proper manner to generate an image having a predefined resolution.
Human visual perception is generally more sensitive to green than the other primary colors. For this reason, CMOS image sensor 10 may be fabricated so that the green unit color cell C3 occurs with greater frequency compared with the red and blue unit color cells C1 and C2, respectively.
With systems using conventional CMOS image sensor 10, the green unit color cell C3, the red unit color cell C1, and the blue unit color cell C2, all of which may constitute the cell array CA, may display only one color associated with the respective photosensitive pixel 30 (i.e., any one of green, red and blue). Thus, as long as each cell does not depend on a differing adjacent color filter cells, it is impractical to realize a variety of colors associated with any single photosensitive pixel 30.
In other words, with conventional imaging systems, only when the red unit color cell C1 is processed with different unit color cells C2 and C3, is it practical to express a variety of colors required for image generation. However, when the red unit color cell C1 is isolated from different unit color cells C2 and C3, imagery representing only the color red can be produced.
In this manner, images expressing all of the colors associated with respective unit color cells C1, C2 and C3 can be produced. However, the processing produces pixels in the final image which are mutually dependent upon light collected from neighboring unit color cells. Because of this mutually dependent relationship, the production of images by photosensitive pixel units 30 can be inefficient. As a result, a final resolution of the image obtained by the image sensor 10 may be greatly reduced over the total number of arranged unit color cells C1, C2 and C3.
That is to say, with conventional systems, even though relatively many unit color cells C1, C2 and C3 are provided, it is impractical for CMOS image sensor 10 to normally obtain a high resolution image which is proportional to the total number of arranged unit color cells.
Obtaining higher resolution images using conventional CMOS sensor 10 would typically entail increasing the number of unit color cells C1, C2, and C3, unless other measures are taken. Consequently, CMOS image sensor 10 may encounter various problems, such as an increased price, increase in size, etc.
Furthermore, in situations where the corresponding image requires a more precise color pattern, the conventional techniques as described above may not be sufficient.
Moreover, conventional CMOS image sensor 10 may be constructed in a manner so that the respective unit color cells C1, C2 and C3 are arranged on the top of intermediate layer 20 in a mosaic type without a separate reinforcement. In this case, when processes for forming additional unit color cells are undertaken without taking separate measures, such as, for example, a process for laminating photoresist, a process for patterning photoresist, etc., the unit color cells C1, C2 and C3 formed previously may be peeled off from the intermediate layer by an impact applied during construction, i.e., the unit color cells may experience peeling phenomena. As a result, the finished color filter array CA takes an abnormal form in which some unit color cells may be sparsely omitted. In this case, it is impractical for the final finished CMOS image sensor 10 to generate a normal image.
Of course, when reinforcements are additionally arranged between the respective unit color cells C1, C2 and C3, the peeling phenomenon of the unit color cells may be prevented to a certain extent, but because the color filter array CA is generally formed on a very small scale, it is almost impossible to additionally provide separate reinforcements between the respective unit color cells C1, C2 and C3 using present process standards. Therefore, the foregoing peeling phenomenon is recognized as a serious shortcoming in the field of known CMOS image sensor fabrication.